Is it or isn’t it? A new study undermines the theory that sex addiction is a brain-based disorder similar to other addictions.

For most of the public, the concept of addiction is pretty straightforward — it involves taking something or doing something that brings you pleasure and that you can’t control. But scientifically, addiction means something much more specific, if not precisely quantifiable.

For much of the 20th century, psychiatrists and laypeople defined addictions as use of substances or behaviors that required ever-increasing doses to maintain a satisfying “high.” These addictions also conspired to form some type of physiologic dependence, which led to physical symptoms such as vomiting and diarrhea when the addictive substance or activity was stopped.

But these criteria failed to capture the compulsive quality of addiction, or the craving that drives relapse long after withdrawal symptoms have dissipated. So today’s expert consensus — as laid out in the psychiatric community’s Diagnostic and Statistical Manual of Mental Disorders (DSM) — defines both substance and behavioral addictions, like gambling, as compulsive behaviors that interfere with normal functioning and continue despite negative consequences.

By that definition, excessive sexual behavior also qualifies as an addiction, and a study published last year found that applying these criteria did indeed distinguish people with sex addictions from those with other psychiatric problems. However, the editors of the latest edition of DSM-5 didn’t believe there was enough evidence to support defining hypersexuality as an addiction and decided not to define it as such in the new volume.

At issue is the broader question of what makes behaviors addictive. Since compulsive behavior may have roots in how the brain interprets rewarding or satisfying behaviors, Nicole Prause, a research scientist at the University of California, Los Angeles, and her colleagues decided to start with brain-wave activity to better understand the nature of compulsive sexual behavior.

They studied 39 men and 13 women, all of whom met criteria for hypersexuality, who responded to ads for a study involving people who had trouble controlling their use of pornography. Each of the participants agreed to have their brain activity measured via a noninvasive electroencephalogram, or EEG, while they looked at pictures ranging from pleasant images of couples caressing to sexually explicit scenes, as well as both pleasant and disturbing images of nonsexual activities. Prior to the brain-wave tests, they also completed questionnaires to assess their levels of compulsiveness and control over their sexual impulses.

The researchers focused on brain-wave patterns that occurred about 300 milliseconds after the participants viewed an image, or p300, which measured how interesting or attractive they found that picture. Previous work involving p300 with drug addicts showed that drug-related pictures were far more compelling than other depictions. Finding similar surges in p300 after the participants viewed sexually explicit images would suggest that excessive sexual activity, like some drug use, might be addictive.

Instead, however, Prause and her colleagues found tolerance — unlike drug addicts, the sex addicts in this study didn’t find the sexual cues more compelling than other images. “They look just like normal people with high sex drive,” says Prause. “People who write about sex addiction would say, ‘It’s not just high drive: they are out of control, they can’t stop and their brains are [changed].’ We just don’t see any evidence for them being different.”

That doesn’t mean that excessive or compulsive sexual behavior can’t be seriously problematic. “I don’t think this means that they don’t deserve help or are faking or just being jerks,” she says. But she thinks adding the label addiction could pathologize normal variation and induce pessimism. “I don’t know that we need the overlay of addiction,” she says.

Rory Reid, a research psychologist at UCLA and a colleague of Prause who was not associated with the study, believes the results don’t close the door on the idea of sex addiction or on hypersexual disorder as a diagnosis. Reid was a principal investigator in research that suggested that the criteria for hypersexual disorder qualify it for a psychiatric diagnosis.

He says that the lack of an association between p300 and measures of sexual compulsion isn’t enough to discredit the idea that it’s a brain disorder. “We can’t really assert that,” he says. Just because p300 doesn’t vary in relation to symptoms like loss of control doesn’t mean that other signals, which Prause’s group did not measure, would not. Reid also suggests that Prause’s participants, who were not in rehab programs, may not have been as severely affected as patients in treatment — and that the images used may not have been extreme enough to generate extra interest the way drug images do in addiction.

Why is it so important to determine whether hypersexuality is an addiction? Reid believes it may be more of a research issue than one that has clinical merit, at least for now. “For the patient who comes in after his third job loss because he can’t stop masturbating to porn at work, he doesn’t care what we call it; he just wants to know how to change and function more adaptively,” Reid says.

But determining if common brain pathways are responsible for sexual compulsion and drug addiction could lead to more effective ways of treating sexual desires that start to interfere with daily life. If sexual addiction is similar to cocaine addiction, for instance, the same medications or talk therapies might be useful and the same brain areas could be targeted for treatment.